The present invention relates to a data transfer method and data transfer system used when data which does not necessitate real time processing such as still image data, document data and the like is transferred between a plurality of apparatuses.
Apparatuses which deal with a still image such as a digital still camera or a printer have been more widely and more increasingly marketed in recent years. These apparatuses are conventionally used in an environment in which a personal computer is present. However, needs for easy handling of such apparatuses in an environment in which a personal computer is not present, is increasing recently.
Conventionally, as a data transfer method when data which does not necessitate real time processing and which is represented by the aforementioned still-image data and document data is transmitted/received between a plurality of apparatuses, a data transfer method in which a control node commands a transmission node and a reception node respectively to control starting/completion of data transfer is proposed in AV/C Compatible Asynchronous Serial Bus Connections, Draft 1.11, Sep. 1, 1998, and xe2x80x9cAV/C Management of Asynchronous Serial Bus Connections, Sep. 21, 1998, in 1394 Trade Association. These method use IEEE Std 1394-1995, Standard for a High Performance Serial Bus, which will be referred to as xe2x80x9cIEEE 1394-1995xe2x80x9d hereinafter, as a bus system, and proposes an asynchronous data transfer method in a form of extending the conventional data transfer control method for transferring/receiving data which necessitates real time processing. According to this data transfer method, when asynchronous data is transferred from a first node to a second node on a bus system in which a node identifier is allocated to each node, a control node sends a command for transfer to the first node and the second node respectively, to thereby improve the command/data processing efficiency.
FIG. 15 is a block diagram which shows a structure of a still image data transfer system using a conventional data transfer method. In FIG. 15, 101 is a data transmission node (a first node) as a device for transmitting an image such as a digital still camera, 102 is a data reception node (a second node) as a device for receiving an image such as a printer, and 103 is a control node such as a personal computer or a set top box, and these devices are connected to the same bus system 100 (IEEE 1394-1995).
FIG. 16 is a system block diagram which describes the operation of transferring data from the data transmission node 101 to the data reception node 102 under the control of the control node 103 in the conventional data transfer method.
Here, an arrow mark 104 represents a data reception command which the control node 103 issues to the data reception node 102, and an arrow mark 106 represents a data transmission command which the control node 103 issues to the data transmission node 101. An arrow mark 105 is a data reception command response by which the data reception node 102 reports the execution result of the data reception command 104 to the control node 103, and an arrow mark 107 is a data transmission command response by which the data transmission node 101 reports the execution result of the data transmission command 105 to the control node 103.
The data transmission node 101 and the data reception node 102 receive the data transmission command 106 and the data reception command 104 issued from the control. node 103, respectively, and by each notifying the execution result to the control node 103, establish the connection and start the transmission of data. Herein, 108 represents data which is transferred from the data transmission node 101 to the data reception node 102.
FIG. 17 is a block diagram which describes the operation of completing the transfer of data from the data transmission node 101 to the data reception node 102 under the control of the control node 103 in the conventional data transfer method.
Here, an arrow mark 109 represents a data reception completion command which the control node 103 issues to the data reception node 102, and an arrow mark 111 represents a data transmission completion command which the control node 103 issues to the data transmission node 101. An arrow mark 110 is a data reception completion command response by which the data reception node 102 reports the execution result of the data reception command 104 to the control node 103, and an arrow mark 112 is a data transmission completion command response by which the data transmission node 101 reports the execution result of the data transmission command 106 to the control node 103. Here, an arrow mark 108 represents data which is transferred from the data transmission node 101 to the data reception node 102.
The data transmission node 101 and the data reception node 102 receive the data transmission completion command 111 and the data reception completion command 109 issued from the control node 103, respectively, and by each notifying the execution result to the control node 103, complete the transfer of data and are disconnected.
However, in the conventional data transfer method above described, the connection between the data transmission node 101 and the data reception node 102 is not disconnected unless the control node 103 gives such a completion command. Therefore, even when the control node 103 has already determined the sheet number of still image to be transmitted, the control node 103 must follow steps of periodically giving commands for asking the situation to the data transmission node 101 or the data reception node 102, and of receiving command responses to the commands, in order to recognize the completion of data transfer which is currently being carried out and command the disconnection thereof. Due to this, an extra command needs to be issued in order to detect completion of the transfer and a command for directing disconnection from the control node 103 is also required, resulting in a poor processing efficiency.
As described above, when a system in which still image data is transferred using the conventional data transfer method is considered, there exists a problem that timing at which data transfer is to be terminated and disconnected is not easily known.
Further, there exists another problem that, as disconnection process is always carried out under the control of the control node, a number of commands has to be issued, resulting in a poor processing efficiency.
The present invention intends to solve these problems and a first object of the present invention is to provide a data transfer system and method thereof in which the automatic disconnection after data transfer directed by the data transmission node or the data reception node is achieved compatible with the conventional disconnection method directed by the control node, whereby the number of commands to be issued is curbed at the minimum, and thus the processing efficiency can be improved.
In addition, a second object of the present invention is to provide a data transfer system and method thereof in which control process can be simplified in a data transfer which is carried out continuously because the completion of the data transfer is easily detected by the control node.
In order to achieve the aforementioned objects, the present invention is characterized in that, in a bus system in which a node identifier is allocated to each node, when a data file is transmitted from a transmission node to a reception node, a control node issues, to the transmission node, a command including an identifier of the reception node and a field value representing a number of data files to be transmitted to execute the data transfer, and in the case where the number of the data files is 1 or more, after the transmission of the data files of the number specified in the field is completed, the transmission node directs the reception node to complete the transfer to thereby complete the data transfer, and in the case where the field value is 0, the transmission of the data files is continued, and thus an automatic disconnection mainly led by the data transmission node or data reception node is adopted after the data transfer.
Thus, there can be obtained an improved data transfer method compatible with a conventional data transfer method, facilitating to confirm a timing of completion of data transfer, reducing issuance of commands to the minimum, attaining a high efficiency in processing.
A first aspect of the present invention provides a data transfer method of transferring at least one data file from a first node outputting a data file to a second node inputting a data file under a control of a control node in a bus system in which a node identifier is allocated to each node, said data transfer method characterized in that: the control node transmits to the first node a first command including the node identifier of the second node, and transmits to the second node a second command including the node identifier of the first node, wherein the first command includes a field which represents a specified number of data files to be transmitted by the first node, and in the case where the filed value is 1 or more, when the first node has completed the transmission of the number of the data files specified in the field, the first node directs the second node to complete the transfer to thereby complete the data transfer, and in the case where the field value is 0, the transmission of the data files is continued.
Thus, in a case in which the number of data files to be transmitted from the first node to the second node has been determined, the timing at which data transfer is to be completed is easily known and the disconnection process is automatically carried out between the transmission node and the reception node, allowing the number of commands issued on the bus at the minimum level. That is, by setting the number of the data files for transmission and reception in the command field, the issuance of the commands is reduced to the necessary minimum by the automatic disconnection mainly led by the data transmission node or data reception node, improving the efficiency in processing.
A second aspect of the present invention is characterized in that, in the case where the field value representing the number of the data files to be transmitted by the first node is 1 or more, when the first node completes the transmission of the data files of the number specified in the field and directs the second node to complete the transfer, the completion of the transfer is notified to the control node.
Thus, the control node can easily detect the completion of the data transfer, and in the case of executing the data transfer continuously, it is possible to smoothly proceed to the next data transfer. That is, after executing the automatic disconnection mainly led by the data transmission node or data reception node, by responding a second response to the control node, the control node easily to detect the completion of the data transfer, and the control process can be simplified in the continuous data transfer.
A third aspect of the present invention provides a data transfer system for transferring at least one data file from a first equipment outputting a data file to a second equipment inputting the data file in a bus system via which a plurality of equipments each having an identifier allocated thereto are connected, said data transfer system characterized by: comprising a third equipment for control which transmits to the first equipment a first command including the identifier of the second equipment, and transmits to the second equipment a second command including the identifier of the first equipment, wherein the first command includes a field which represents a specified number of data files to be transmitted by the first equipment, and the second command includes a field which represents a specified number of data files to be received by the second equipment, and in the case where the filed value representing the number of the data files to be transmitted and received is 1 or more, when the transmission and reception of the data files of the number specified in the fields is completed between the first equipment and the second equipment, the completion of the data transfer is directed to each other between the first equipment and the second equipment, whereby the data transfer is completed without intermediation of the third equipment, and in the case where the field value is 0, the transmission and reception of the data files is continued.
In this construction, the first equipment notifies the second equipment of the completion of the data transfer and the second equipment notifies the first equipment of having recognized the completion of the data transfer, whereby the connection between the equipments is automatically disconnected and the address spaces for transmission and reception of each equipment are cleared.
In this construction, in the case where the field value representing the number of the data files to be transmitted and received is 1 or more, when the transmission and reception of the data files of the number specified in the fields is completed and the completion of the transfer is directed to each other between the equipments, the first equipment or the second equipment notifies the third equipment for control of the completion of the transfer.